Automatic sprinkler systems are some of the most widely used devices for fire protection. These systems have sprinklers that are activated once the ambient temperature in an environment, such as a room or building exceeds a predetermined value. Once activated, the sprinklers distribute fire-extinguishing fluid, preferably water, in the room or building. A sprinkler system is considered effective if it extinguishes or prevents growth of a fire. The effectiveness of a sprinkler is dependent upon the sprinkler consistently delivering an expected flow rate of fluid from its outlet for a given pressure at its inlet.
An automatic sprinkler may be configured for addressing a fire in a particular mode such as for example, control mode or suppression mode. One form of suppression mode is Early Suppression Fast Response (ESFR) which is defined under industry accepted standards, such as for example, the National Fire Protection Association (NFPA) standard entitled, “NFPA 13: Standards for the Installation of Sprinkler Systems” (2013 ed.) (“NFPA 13”), Section 3.6.4.2 as a sprinkler having a thermal sensitivity, i.e., response time index (“RTI”) of 50 meter1/2 second1/2 (“m1/2 sec1/2”) or less and “listed” for its capability to provide fire suppression of specific high-challenge fire challenges. A “listed” sprinkler for fire suppression is a sprinkler that has been tested, verified and published in a list by an industry accepted organization, such as for example, FM Global (“FM”) and Underwriters Laboratories (“UL”) as a sprinkler being suitable for the specified purpose of fire suppression. Fire suppression is defined by NFPA 13, Section 3.3.12 as “[s]harply reducing the heat release rate of a fire and preventing its regrowth by means of direct and sufficient application of water through the fire plume to the burning fuel surface.” UL and/or FM test and verify fire suppression performance of a sprinkler by at least installing and subjecting the sprinkler to their respective water distribution test standards: (i) FM Approval Standard Class No. 2008 (2006), which is attached to U.S. Patent Application No. 61/724,843; and (ii) UL Standard for Early-Suppression Fast-Response Sprinklers UL 1767 (2010), which is attached to U.S. Patent Application No. 61/724,843.
The ESFR test standards and requirements for suppression are generally related to the K-factor of the sprinkler. The discharge coefficient or K-factor of a sprinkler allows for an approximation of flow rate to be expected from an outlet of a sprinkler based on the square root of the pressure of fluid fed into the inlet of the sprinkler. As used herein, the K-factor is defined as a constant representing the sprinkler discharge coefficient that is quantified by the flow of fluid in gallons per minute (GPM) from the sprinkler outlet divided by the square root of the pressure of the flow of fluid fed into the inlet of the sprinkler passageway in pounds per square inch (PSI). The K-factor is expressed as GPM/(PSI)1/2. NFPA 13 provides for a rated or nominal K-factor or rated discharge coefficient of a sprinkler as a mean value over a K-factor range. Chapters 3, 12 and Sec. 6.2-6.5 of Chapter 6 of the 2010 edition of NFPA 13 are attached to U.S. Patent Application No. 61/724,843. For example, for a K-factor greater than 11, NFPA 13 provides the following nominal K-factors (with the K-factor range shown in parenthesis): (i) 14.0 (13.5-14.5) GPM/(PSI)1/2; (ii) 16.8 (16.0-17.6) GPM/(PSI)1/2; (iii) 19.6 (18.6-20.6) GPM/(PSI)1/2; (iv) 22.4 (21.3-23.5) GPM/(PSI)1/2; (v) 25.2 (23.9-26.5) GPM/(PSI)1/2; and (vi) 28.0 (26.6-29.4) GPM/(PSI)1/2. For purposes herein, suppression performance can be determined for sprinklers having K-factors not listed in the test standards by an appropriate equivalent requirement extrapolated from the available test standards. Moreover, suppression performance may be determined by other criteria in addition to or alternatively to the ESFR test standards, such as for example, by the hydraulic design criteria of the sprinkler and more specifically the hose stream demand criteria.
While ESFR sprinklers are defined by the RTI of the sprinkler and its performance under the test standards, it should be understood that “suppression” mode sprinklers are not necessarily limited to ESFR sprinklers or sprinklers having an RTI of 50 or less. Accordingly, suppression mode sprinklers satisfying standardized test and/or other suppression criteria may have a thermally sensitive trigger having an RTI of fast or standard response sprinklers, i.e., RTI of 50 or greater.